The coefficient of thermal expansion (CTE) of the prepreg systems in composite materials during autoclave curing is recognized to significantly influence the development of internal stresses within composite structures, the dimensional stability of cured components, and the accuracy of structural profiles. To accurately measure the CTE of composite prepregs under autoclave curing process temperatures, a non-contact high-temperature CTE measurement system was established by combining a monocular optical measurement setup with a constant-temperature heating platform, based on the digital image correlation (DIC) method. The system applied thermal loading to the composite prepreg according to the curing process temperature profile, and image data at different curing stages were captured by a camera. Thermal deformation was extracted via DIC technology, from which the CTE was calculated. The system’s accuracy was validated by measuring polyetheretherketone a standard reference material with a known CTE. The mean value from three measurements was 52.4×10^-6 K^-1, which reduced by 2.78% from the standard value of 53.9×10^-6 K^-1, demonstrating that the system meets accuracy requirements. Subsequently, the non-contact high-temperature CTE measurement system was employed to determine the CTE of carbon fiber-reinforced polymer composite prepregs at curing temperatures, and the results were further verified using finite element analysis. The findings demonstrate that the system enables rapid and accurate measurement of the CTE of composite prepregs under autoclave curing temperatures.